As typical structures of a semiconductor package (semiconductor device), there have been known a package structure using a lead frame as a circuit base on which semiconductor chips are mounted (TSOP (Thin Small Outline Package) and the like) and a package structure using a wiring board as a circuit base (BGA (Ball Grid Array) and LGA (Land Grid Array)). A semiconductor package such as TSOP contributes to cost reduction of the semiconductor package since it uses an inexpensive lead frame as the circuit base.
TSOP has a resin-sealed body in which semiconductor chips mounted on the lead frame are resin-sealed and outer leads projecting from side surfaces of the resin-sealed body. The size of the resin-sealed body enclosing the semiconductor chips is smaller than the package size of TSOP. Therefore, the size of the semiconductor chips is unavoidably smaller than the package size. When the semiconductor package is mounted on a mounting board, an actual shape of the semiconductor chips becomes smaller than an area occupied by the semiconductor package on the mounting board. In a semiconductor package having semiconductor memory chips such as NAND flash memories, it is not possible to obtain a memory capacity corresponding to the package size.
A semiconductor package such as BGA or LGA can have larger semiconductor chips packaged therein than TSOP since the size of its resin-sealed body and its package size are equal. However, a mounting board for TSOP (printed circuit board or the like) is not usable as it is for BGA and LGA since in typical BGA and LGA, external connection terminals are disposed in matrix on a lower surface side of the wiring board. BGA and LGA are mounted on mounting boards having terminals compatible thereto. When BGA or LGA is applied in place of TSOP, BGA or LGA is preferably designed so as to be mountable on an existing TSOP mounting board in view of general versatility. For this purpose, the arrangement of the external connection terminals of BGA or LGA has to be the same as the arrangement of the outer leads of TSOP.
In BGA or LGA, arranging the external connection terminals along two opposite outer sides of a wiring board similarly to the outer leads of TSOP unavoidably necessitates narrowing the pitch of the external connection terminals and thus involves a possibility of the occurrence of various problems. The use of the external connection terminals of conventional BGA or LGA as they are involves a concern about deterioration in mounting reliability. If the external connection terminals of BGA or LGA are formed at about the same pitch as the lead pitch of TSOP so that BGA or LGA is TSOP-compatible, the narrowed pitch of the terminals gives rise to various problems.
JP-A 2000-082757(KOKAI), JP-A 2003-332497(KOKAI), and JP-A2006-294656(KOKAI) describe that connection terminals disposed at corners are made larger than connection terminals disposed in an inner area in order to enhance mounting reliability of BGA. In all of these techniques, it is premised that the connection terminals (BGA terminals) are arranged in matrix, and there is no idea of arranging the connection terminals along two opposite sides of a wiring board. Nor is there any idea of forming the connection terminals at about the same pitch as the lead pitch of TSOP.